Synthetic resin films or sheets, which reflect light, have been conventionally used for backlights of electrical spectacular signs, lighting apparatuses, displays, or the like. For example, light reflecting plates, which are obtained by processing synthetic resin films or sheets into stereoscopic shapes in order to suppress brightness unevenness, have been proposed (for example, see Patent Literature 1).
However, when the thermoplastic resin foam films or sheets are processed into stereoscopic shapes, the films or sheets are deformed due to strain in molding or constriction after molding. Accordingly, a means has been proposed, which prevents a light reflecting plate from deforming by fixing a light reflecting plate subjected to shape processing and a metallic casing (For example, see Patent Literature 2).
In recent years, power saving and high efficiency have been required in the fields of lighting apparatuses, liquid crystal displays, and the like. Therefore, a resin film or sheet having a higher reflectivity has been desired. In particular, needs for space saving has been enhanced in the fields of electrical spectacular signs and displays, and it has been required to make a resin film or sheet, which reflects light, thinner. It is hard to make the above described light reflecting plate meet the requirements when making a thinner product.
Accordingly, a thermoplastic resin foam film or sheet having many fine bubbles or pores in the inside thereof has been proposed as a synthetic resin film or sheet, which reflects light (for example, see Patent Literature 3). The thermoplastic resin foam film or sheet has a mean bubble diameter as fine as approximately 10 μm, and therefore exhibits a high reflectance.